Machine for drawing and trimming thermoplastic containers



Jan; 13, 1942. F, DUL 2,270,187

MACHINE FOR DRAWING AND TRIMMING THERMOPLASTIC CONTAINERS Filed Oct. 4,1940 Patented Jan. 13, 1942 'MACHINE FOR'DRAWING AND TRIMMINGTHERMOPLASTIC CONTAINERS Frederick .E. Dulmage, Midland,Mich-.,assignorto The Dow Chemical Company, Midland, Mich., a corporation ofMichigan v Application October 4, 1940, Serial No. 359,774

This invention relates to a machine for making drawn containers and thelike from thermoplastic organic films, and for trimming said containers,all in a single operation.

Thermoplastic films have been drawn heretofore. It is an almostinvariable result that the shaped article, when removed from the drawingdevice, has a fluted or ruffled edge which must be removed. The trimmingof the ruffled edges of such containers has ordinarily constituted aseparate operation.

It has been proposed, however, both to shape and trim such drawnarticles in a single operation by means of a machine comprisingthe usualdie and ram, in which the ram is provided with a slightly enlargedsection above the working section thereof, forming a sharp-edgedshoulder to cooperate with the edge of the die opening so as to out offthe formed piece after it has been shaped by the ram. Such a devicesuffers from the fault that with a given ram the depth of the cut-offarticle cannot be varied, and also has the further disadvantage that theadjustment of the diameter of the cutting-off section of the ram to thatof the die opening is so fine that it can be easily disrupted by theexpansion or contraction of the parts caused by variations intemperature during working. A slight contraction of the ram may cause itto slide in the die, without cutting off the work cleanly, while aslight expansion may cause it to jam in the die or to strike on the edgeof the die opening with consequent damage to the machine.

It is accordingly among the objects of the present invention to providea machine for making drawn containers and the like from thermoplasticorganic films and for trimming said containers all in a singleoperation, without the requirement for such precise temperature controlas has heretofore been necessary in machines of this character. Anotherobject is to'provide a machine of the type above mentioned, whichmachine is not limited as to the variety of depths of articles which canbe drawn therein. Other and related objects will appear hereinafter.

To the accomplishment of the foregoing and related ends, the invention,then, consists of the means hereinafter fully described and particularlypointed out in the claims, the annexed drawing and the followingdescription setting forth in detail certain means for carrying out theinvention, such disclosed means illustrating, however, but several ofthe various ways in which the principle of the invention may be used.

In the said annexed drawing-'- Fig l is a view in typical verticalsection of one modification of a machine whereby the foregoing objectsmay be attained;

Fig. 2 is a detailed View in section of a particular modification of anelement of the machine illustrated in Fig. 1; and

Fig. 3 is 'a view in vertical section through a particular modificationof the trimming edge and. die member in said machine.

Referring now to the drawing, a vertically mounted shaft I4 carrying aplunger I 3 which fits into the opening I2 of a female die I I with onlyan amount of clearance equal to about twice the thickness of the film I5to be drawn plus a factor of approximately 2 mils, is driven in avertical direction by a press, not shown. A clam-ping ring I0, somewhatlarger in internal diameter than, and concentrically disposed withrespect to, the opening I'2 in die II,'is provided for holding film I5initially fiat across the said opening l2. Sufiicient pressure isapplied to ring II! in known manner, by means not shown, to resist thewrinkling of the film which ordinarily accompanies drawing operations,while still allowing film I5 to slide from beneath the ring In under thetension caused by the downward movement of plunger I3 into the dieopening I2. Over the piston or plunger I3, and slidably mounted on shaftI4, is a knife I6, the function of which will be described hereinafter.Above knife I6 is hammer I'I releasably mounted on shaft I4. Abovehammer H on shaft I4 is tension spring I8 held in position by stop I9.

The annular knife I6, having a sharpened cutting edge 20, slides freelyon shaft I4 and is of such dimension that, when plunger I3 is loweredinto opening I2 of die'l I, the said knife rests on the shoulder points25 of the die.

The hammer I1 is held on shaft I4 by pawl 2| which engages notch 22 solocated that spring I8 is compressed between hammer I1 and stop I9. Pawl2| is connected with a trip mechanism 23, which is adjustable as toheight.

The shaft I4 and plunger I3 may be bored axially to provide a conduit 24through which a blast of compressed air or other fluid may be driven todischarge the shaped article from the die at a suitable point in thecycle of operations.

In operation, plunger I3 is raised above the level of the heated die IIand a suitably pre-cut blank of thermoplastic film I5 is clamped flat bymeans of ring I0 over the die aperture I2. Hammer I1 is mounted withrespect to shaft I4 in the elevated position illustrated in Fig. 1.Plunger I3 is then lowered on the down stroke into aperture I2, plusdrawing the film I5 into the die II. The knife I6 rides downwardly onplunger I3 until it rests on the shoulders 25 of die II. As the plungerI3 is lowered further, the trip mechanism 23 releases pawl 2| from notch22 and the hammer I1 is propelled by spring I8 to strike the knife Hi.The film I5 is thus out between the knife edge 20 and the shoulder point25 of die II and the fringe of the film blank remaining under-clampingring I0is thus severed from the shaped portion of the film. The plungerI3 continues its downward path until it has passed completely throughaperture I2 at which time the shaped container iseasily removed,suitably with the aid of an air blast directed through the conduit 24.At the same time, spring I8 is compressed against ham mer H by thedownward motion of stop I9 until pawl 2I again engages notch 22. At thispoint plunger I3 is raised on the return stroke once more above thelevel of die II carrying with it knife I6, and the machine is ready foranother cycle of operations.

Fig. 2 shows a preferred form of the shoulder point or rim 25 of die II.The shape of shoulders 25 illustrated in Fig. 2 prevents any scoremarks, made by the impact of the knife I6, from scratching the foil asit is drawn past the contact surfaces of die II.

The die and co-acting ram and cutting member may be of any desiredcross-sectional contour, to form round, oval, square, or other polygonalarticles from thermoplastic films.

Iclaim:

1. A machine for drawing films and for trimming the drawn article,comprising a perforate drawing die and a drawing ram co-operativetherewith to shape a thermoplastic film, a cutting member slidablymounted on the ram and having a cutting edge of the same peripheralcontour as the ram and the die opening, positioned to engage the die tosever the film remnant disposed around said opening from the drawn filmwithin the opening, a trip hammer slidable on and releasably engagedwith said ram a predetermined distance away from the cutting member andon the side thereof away from said die, means for releasing the hammerfrom engagement with the ram when the latter has penetrated the desireddistance into the die and the cutting member has come to rest on thefilm, and means for impelling the hammer against the cutting member andfor holding the cutting member, securely against the die during motionof the ram into the die after the drawn article has been trimmed.

2. A machine for drawing films and for trimmingthe drawn article,comprising a horizontally disposed drawing die with a vertical openingtherethrough, a drawing ram co-operative therewith to shape athermoplastic film, a cutting member slidably mounted on the ram andhaving a cutting edge of the same peripheral contour as the ram and dieopening, positioned to engage the die to sever the film remnant disposedaround said opening, a trip hammer slidable on and releasably engagedwith said ram a predetermined distance above the cutting member, meansfor releasing the hammer from engagementwith the ram when the latter haspenetrated the desired distance into the die and the cutting member hascome to rest on the film, and a spring, compressed when the ram andhammer are engaged, serving to propel the hammer sharply downwardagainst the cutting member, and then to hold the cutting member securelyagainst the die during motion of the ram into the die after the drawnarticle has been trimmed.

FREDERICK E. DULMAGE.

